In recent years, LED lamps have come to be used for car headlights. A high-power LED chip is used for a vehicle-installed LED lamp, wherefore a substrate for the mounting of the LED chip is required to have high heat-dissipation capability. Thus, heretofore it has been customary to use an aluminum nitride substrate having high thermal conductivity for a vehicle-installed LED lamp. However, at present, there is an increasing demand for a substrate which has high thermal conductivity and yet is inexpensive to manufacture. An example of such a substrate is disclosed in Japanese Unexamined Patent Publication JP-A 2007-165751.
The substrate disclosed in JP-A 2007-165751 is constructed by forming an alumite layer on the surface of an aluminum substrate, forming cracks in the alumite layer by, for example, application of thermal stress, and forming a thermally-conductive resin insulating layer on the surface of the crack-bearing alumite layer.
However, the thermally-conductive resin insulating layer is formed of resin and thus exhibits hygroscopicity, wherefore ion migration may occur. Furthermore, due to a large difference in thermal expansion coefficient between resin and alumite, the alumite layer and the thermally-conductive resin insulating layer may be separated from each other under thermal history, which results in deterioration in thermal conductivity.
The invention has been devised in view of the problems as discussed supra, and accordingly an object thereof is to provide an electronic component mounting substrate which excels in resistance to migration, and is thus capable of maintaining high thermal conductivity and insulation performance for a long period of time, and also provide a light emission device using the electronic component mounting substrate.